If you think your conlang will ever be as big of a thing as Lojban, you need a serious reality check. Besides, being successful is a legal danger all by itself because then every sleazy lawyer in the world will pelt you with lawsuits just in the hopes of one of them sticking so they can pump money out of you.
Besides, if I understand the information in the link correctly, the only reason copyright claims entered the picture at all was because of a schism between the (multiple) creators of the project. If you're working on a conlang by yourself, this can't happen.
They can't copyright the RTS system or the premise of taking control of a historical civilization however. If you're really concerned you can A) write to them and ask for specifics (probably a waste of time) or B) simply look up similar games for a feel of what they were allowed.
Actually I'm afraid that they can (though it would be a patent, not a copyright). The US policy on patents is pretty much universally "approve first, ask questions later" and the law is strongly biased against the defendant in infrigement claims:
- Independent invention is not a defense in claims of patent infringement (it is, however, a valid defense in claims of copyright infringement). If they filed before you invented independently, you're in violation.
- The burden of proof is on the defendant that they didn't
violate the patent, or that they were using the patented design before the plaintiff.
- The defendant doesn't have to be a direct competitor to the plaintiff for there to be a violation. In fact, the plaintiff doesn't even need to be using the patent at all for it to be valid. Companies thus have every incentive to file as many patents as possible, as broadly as possible. There even exist companies who don't produce anything at all: Their entire business model is to file/acquire patents and sue others.
Your particular example of the RTS genre, or the premise of taking control of a civilization, would not hold up in court because people have been making those games for years. However, if not for that, you could almost definitely patent them and sue infringers successfully.