starting a service based on someone's GPL/MIT licensed code

Question

someone wrote a nice framework for developing html5 3d engine. It's GPL/MIT licensed. Do you think it's a good idea to build upon it, and then repackage it and sell it as a service?

For eg> the framework lets you build 3d environments. so I build on it, maybe add a few features like characters and music in the environment, and turn it into an online game.

Is it a feasible idea?

Of course, part of the GPL license says that all source code has to be visible to end users.

Assuming the web is a winner take all market based on first mover advantage, why care about hiding the source code? It's the product that's being sold that counts.

Answer 1

It's my understanding that dual licensing means that you're free to choose whichever license you want and abide by that license's restrictions.

So, if the product you're looking at is dual-licensed under the GPL and MIT licenses, then you can choose to abide by the MIT license's restrictions (which are almost nil) and do not have to release source code as required by the GPL.

jQuery is the best known MIT/GPL dual-licensed project. The jQuery licensing page says (emphasis added):

You may use any jQuery project under either license... The MIT license is recommended for most projects... [It] places almost no restrictions on what you can do with a jQuery license... You don’t have to do anything special to choose one license or the other and you don’t have to notify anyone which license you are using. You are free to use a jQuery project in commercial projects as long as the copyright header is left intact.

This is, however, merely my understanding; you may wish to consult a lawyer to be certain (especially if this is a serious business venture, and you make it sound like it is).