Second Life vs. OpenSim

You cannot compare Second Life and OpenSim. One is a social world. The other is an open source piece of server software.

You can’t even compare Second Life to individual grids using OpenSim as their backend software. Second Life has around a million users logging in each month, while the most active OpenSim-based grid, Avination, has just 9,000. There are an average of 50,000 Second Life users on at any one time — in Avination, there might be as many as a couple of hundred.

So, really, no comparison.

But it’s a holiday weekend, so I’m going to compare the two, anyway.

Second Life OpenSim
If you’re looking for a social group, you can find anything you want. Political activists. Role players. Educators. Artists. Designers. Sexual minorities. If you already have a group, you can bring your group to a grid — or start your own grid.
Large user base for event promoters looking for audiences, retail merchants looking for customers, marketers looking for influence, and activists looking for publicity. Small groups of widely dispersed users. Some merchants may find niche pockets of under-served customers on new grids.
$295 a month per region, plus $1,000 setup fee. Texture uploads cost money. Free if you run it on your own computer or USB stick. Starting at $9.95 a month per region with no setup fee for professional hosting. Up to $100 a month for a high-performance region, or on a high-end commercial grids. Texture uploads are typically free.
Unreliable for mission-critical business meetings due to problems with voice, unexpected region crashes or restarts, login problems, lag, and other issues. But stable enough for classes, in-world talk shows, fund raisers, and social gatherings. Some enterprise users report higher stability than Second Life, due to high-end hardware and plenty of bandwidth. Typical commercial grids have less stability, however. Open grids — where users can connect regions hosted on home computers — can have extremely poor performance and stability on those regions. Grids running older software can also have instability issues due to bugs that have since been fixed. Grids running untested, experimental versions of OpenSim can also suffer due to the appearance of new bugs that haven’t yet been fixed.
Lots of content available both through in-world merchants and freebie shops and through a gigantic web-based marketplace. Content slowly becoming available from in-world merchants on commercial grids and for download from websites. As grids mature, infringing content in freebie stores on open grids is discovered and removed, and replaced with non-infringing original content. Some merchants beginning to offer DRM-free content on websites and in hypergrid-enabled shopping areas.
Some content protection and digital rights management technology available to protect content creators, but content theft is still frequently reported. Content protection is completely up to the grid owner. Some commercial grids, including Avination and InWorldz, have the same level of content protection as Second Life. Other grids offer more freedom to users, allowing them to back up their inventories or regions. Private grids run by companies, schools, groups or individuals can put as much or as little content protection in place as they want or need.
Linden Lab owns all the content in Second Life. Users just get a license to use it. Linden Lab can remove individual items from user inventories, entire regions from the grid, or shut down any user account at any time. Individual grid owners determine the content use policies on their grids. Some commercial grids follow Linden Lab model. Others allow their residents to have rights to their content. Meanwhile, companies, schools, groups and individuals who run their own grids have full ownership of those grids — similar to the way they have full ownership of their websites.
Linden Lab allows individual users to make backups of content in which they themselves have created every part of the object. Individual grid owners determine backup policies. Some, like InWorldz and Avination, mirror those of Second Life. Other grids allow more backup options. Owners of private grids can backup any objects, can make backups of entire inventories of individual users, of entire regions, or of the whole grid.
All Second Life land is provided by a single vendor, Linden Lab. However, resellers and middlemen may step in to subdivide or improve virtual land. More than 50 different vendors rent land on individual grids or as standalone regions, mini-grids, or run full grids for customers —  not counting in-world developers who subdivide and resell land in individual commercial grids.
Second Life uses the commercial Havoc physics engine. OpenSim grid owners can take advantage of OpenSim’s modular nature to use any of a number of either open source or commercial physics engines. Most OpenSim grids tend to use the default physics provided with the OpenSim software, ODE, which is inferior to that available in Second Life particularly when it comes to vehicle physics.
Second Life uses LSL, the Linden Scripting Language. OpenSim currently supports more than 95 percent of all LSL commands, and adds a number of unique OSSL commands. Users can also write their own scripting commands and include them as an OpenSim module — or create a completely new scripting engine. InWorldz, for example, has deployed its own scripting engine, called Phlox.
Second Life uses a voice system from Vivox. Grid owners can also choose to install modules for a couple of different free voice systems, including Freeswitch and Whisper/Mumble, or buy a commercial license. Avination, for example, has a license to Vivox, the same voice system used in Second Life.
Second Life uses the Linden dollar currency. Users can also make off-grid transactions via PayPal or PayPal Micropayments. OpenSim grid owners can create their own in-grid currency. Many commercial grids, including Avination and InWorlds, have done this. As long as all regions on the grid are hosted by the grid owners, this is as secure as the currency system in Second Life. OpenSim grids can also install modules that use the multi-grid OMC currency from Virwox, or enable in-world payments via PayPal or PayPal Micropayments. With both OMC and PayPal, final confirmation of transactions take place on a webpage, for maximum security.
There are several third-party exchanges that trade Linden dollars for US dollars or Euros. However, officially, the currency is not actually owned by users but is licensed, and Linden Lab can terminate that license at any time without a refund. The OMC currency can be traded for US dollars, Euros, and Linden dollars on the Virwox exchange. It is accepted on 28 different grids, and if a particular grid goes out of business, the currency will still retain its value. Avination’s currency is also now traded on Virwox, but is unlikely to retain value if the grid closes. Other in-grid currencies can only be bought from their grid owners and may or may not be redeemable in the future.
Teleports only between regions on the Second Life grid. Teleports between any hypergrid-enabled grids by using a hypergate, link region, or simply entering the hypergrid address in the Map dialog’s search field. Currently, hypergrid teleports are limited — it doesn’t work between grids running versions of OpenSim that are too far apart, or between regions located too far apart on the map, and doesnt support friends or instant messages. These limitations are expected to be addressed in future releases.