Perens was hit with the lawsuit last year by Open Source Security which is its trading name; it is better known as Grsecurity and sells a hardening patch for the Linux kernel.
Grsecurity and its owner, Brad Spengler, were offended at Perens' characterisation of its efforts as presenting "a contributory infringement and breach of contract risk" and sued him in August last year.
This law deals with legal complaints that are directed at stopping public discussion and free speech. California put in place an anti-SLAPP law in 1992.
Spengler and his group have appealed the verdict to the US Ninth Circuit Court of Appeals; they had sought US$3 million in damages in the original lawsuit.
Perens had sought US$526,893.50 as his costs but Magistrate Judge Beeler cut this down to US$259,900.50 in costs and US$2403.12 for costs.
She said the money should be paid right away, denying a request by Spengler's lawyers that it be payable only after the appeal was decided.
iTWire has sought comments from Grsecurity.
Link to judgment: courtesy The Register