patents make GIF the most safe for use today

The common technique is to keep applying for more patents on a underlying technology that builds on the old patents as soon as the old ones are nearer to the expiry date therefore keeping it patent encumbered forever. For instance, a patent on rendering GIF images faster might be patent encumbered and that particular optimization might be in common use. GIF is unlikely to be of that much interest to pursue this path but other more high profile stuff like multimedia codecs are likely following this strategy.