Free models are models saved on the ROBLOX website that others are free to use in their places. When building, you can access the free models by clicking insert and selecting "Free Models" from the drop down menu on the right. They are quite controversial, and many people are flamed or trolled for using them, as they believe the use of free models indicates a lack of effort on the creator's part because they used another person's work (often without giving credit to said person) instead of creating it by themselves.
As of late 2008, and so forth; certain types of free-models are known to contain "Infection" scripts, which mostly change the name of objects, or mass copy/delete items, thus causing lag. Being that way, people who have been around for awhile tend to stray away from them. "Infection" scripts have been known to mostly inhabit "Anti-Viral" scripts, "Anti-lag" scripts, admin commands, tool givers, and the tools themselves. Sometimes if you added a free model to a place, it may go crazy and say things like "DESTROY ROBLOX", "You're getting haxed.", and "Telamon Rules." These are also called Viruses and have the same function. A good way to make sure a model doesn't have a virus or any type of infection is to check all the things that are in the model. Most are found in the form of a weld and the name of the weld often says "OH SNAP YOU GOT INFECTED! XD", most of the times if you find this in some of the free models nothing noticeable happens but be sure to delete it just to be safe.
Free models are copied often, and they're infected also. A good example being Wh1tetip's Orb V1, which was made in November 2011. Ttyyuu12345, and a few others infected the model, making it to where if you place it now, it contains several infected items.Free models also have received harsh criticism from certain users. Many games which have multiple free models are insulted, as are the creators of these types of games, for example, SONICTHEHEDGEHOGXX's Live in a Five Star Island Resort. Using Free Models is fine, but, don't make it obvious! You will be most likely disrespected and have bad comments.
Free models are often used in group places also, but most of the time the group place owner says that they did no such thing.
If you just look in the free models though, you can find stuff from or similar to their place, that's where they got their place from and attempted to re-color or remodel everything, such as a gun.