... but I always like the idea to "outsource" processing to client side
I see, but the PCDTR needs no JS enabled to run clientside.
That's an advantage.
... And from what I've seen until now it seems a better option than plain image replacing especially since the script "transforms" the existing H1 tag instead of replacing it with an image.
The Transformation is given anyway. The H1 (and all Replacements) Tag will be replaced anyway - not on the fly, but also using CSS as a operating base.
The "on the Fly" replacement of PCDTR is only given at the first run. After the image is created, it will be saved to a folder and (lightweight png's) the next time they are called from the cache.
Another Advantage is, that you can use different fonts by just using the CSS File - as you would normally do for other CSS - just ensure you have the Font in the directory (use AFE i.e.) and go.
I don't know about the license thing, but it would be nice if someone could make a frontend filter out of it.
The license doesn't inspire me to create such a filter...
I prefer to use the PCDTR Filter instead.
It's easy to set up and run.