yes its illegal,
what won't happen, unless you game becomes a really big hit, you most likely won't be sued, unless you refuse to comply with a cease and desist order.
what will happen, if the don't like what your doing they will send you a cease and decist order demanding that you stop distributing their stuff, if you fail to comply they will sue.
i don't think companies are quite at the level of villiany yet to go after somebody sharing the resurces with a friend. free distribution and they might get a little edgy.
Conclusion,
using thier stuff is not a good idea. don't if you can help it.
