Just to add some more speculation, I remind you that there is one commercial game out there based on the SRDs, and clearly very well known to Issaries as the publisher also publishes one zine and one HQ supplement for Glorantha.
Taking this fact into consideration, I doubt the SRDs can or will be declared invalid per se. At least one of them is absolutely and thoroughly valid (the core book is declared as OGC and has no reference to Glorantha in it). I think I should go look for a copy of the Companion SRD with the OGC declaration in it, as I might need that part of the rules for a project of ours that is in progress. But that is all.
OTOH, as the work you are working on is intentionally targeted at Glorantha, Vile, I think the best solution for you is to just wait for lawstaff's opinion about the subject.
That said, I think I am going to have a loooong talk with Jeff about the subject at Castle Stahleck. Luckily, this will allow me to drown the legal nuisances into some fine German ale.