IMHO, Tom you are comparing apples to oranges. The original SG movie creators would still get a % of the new series, but the creators of the new characters in the SG1 TV series would not and only would get compensation for those SGA episodes in which they appeared in the spinoff, not for the entire production run. That's why you don't see Sam and Teac in the premire episode. The Sam and Teac creators can argue that their characters are essential to the success of the spinoff and should be entitled to share any profits. Conversely, BSG wasn't really a TV series spawned from a movie and the BSG creators are the same people. Unless Universal sold the character rights to Larson, they should be free to use whatever characters that were created during the original run.
It's the main reason many actors/producers/etc set up their own production and distribution companies to control the money.
Read the participation in profit section here:
https://www.realityshowpitch.tv/what%27s_the_deal$.htm
Hollywood Options:
https://www.hollywoodcomics.com/optionagr.html
Everything depends on the contract. Some contracts have an escape clause, where the rights revert to the creator IF the studio does nothing with the property for a set period of time and declines to use it after you inform them to use it or lose it. Most studios want total ownership, merchandising, dvd, remake/sequel rights, book deals, etc. etc. You need a team of lawyers to secure and insure you are getting everything you should and when.
So what they are doing in SGA is just limiting the amount of money to be paid out. Can read some of the disappointment by the original writer and producer of the Stargate Movie (Devlin and Emmerich) when MGM declined to fund their trilogy and opted for the TV series. Just do a search and you'll find plenty of interviews. Gateworld's is below:
https://www.gateworld.net/news/movienews.shtml
Not many fans of the SG1 TV series would agree, but the original SG movie fans feel they lost a golden opportunity to see more Earth mythos being explored and the original SG actors (Spader and Russell) back in action.