Ok, so maybe the answer is for someone to contact the right people at HTC and find out for sure if they do in fact own the patent in question. If we find out that they are the legal owners of the patent, then due to HTC and Mesa both being part of the OIN, Mesa can freely use the S3TC patent.
That may be true but if a participant in the OIN was withholding patents then wouldn't the patents being withheld be referenced on the OIN web site?
The thing of it is that the S3TC patents are big money due to licensing and royalties from hardware that uses it and we don't know what the status of S3TC tech is after HTC bought S3 Graphics, which was already owned by HTC's parent company, The VIA Group. It may be that the S3TC patents were purchased by HTC and then transferred to VIA Technologies or some other company in The VIA Group, which means that OIN has absolutely no reach in such an instance as only HTC is a member of OIN. Until someone probes HTC for information about the current state of things - which I don't think anyone has bothered to do - there can be no S3TC implemented in Mesa.