I  have to deliver the project by the end of June. Running Beta is one thing, have it running  on  a standard (latest) version is another.

that's what i meant by included. 

When will you be delivering the project? 

What do you mean by it needs to be included in it?

At least i used to be a  beta tester. Don't know  at present. i run 3.2 7.b8 (Intel)

But i will need it for the  Standard Version as I'm working on a quite complex project in which it needs  to be included.

best

change font, size and  position

 I haven't seen any glsl that can do this exactly.. some render fonts for sure, but I don't think they can load system fonts etc.

Rendering fonts is a processor intense process, and this is why you are seeing some latency. Generally I recommend to render your font/text via the Text Draw actor at a larger size and animate the text (scale location etc) via Matee++ (this animates as a bitmap, so no redrawing).

Are you seeing the Frame Rate in Isadora drop? (is this the latency you mention?)

One possible workaround would be to use the new Pythoner actor (in Beta currently) to render the text.
This would solve the framerate slow down because Pythoner runs in a Thread Parrallel to Isadora. This means you could ask the Pythoner actor to render something that takes 2 seconds, and it will not slow down the scene processing of Isadora, because it simply doesn't return a value until it is ready (seconds later).

So given your use-case, it is likely that a frame or two will process in Isadora while the text is being rendered but no delay in playback animation etc will be seen (assuming the text render is used for content, font, maybe size).. the text will update the frame or two later.
NOW I would still recommend to do XY animation via Matte++ to cut down on the amount of rendering, and because that animation might be seen more if it does to say 15fps for rendering. 

This is an interesting use case.... so I will see if I can come up with a example file

@gapworks are you a Beta Tester?

UPDATE: I have a working Python example.. however, it doesn't perform as well as I had hoped. With that said, I circle back to what I mentioned about breaking up the animation so that Matte++ does as much of your animation work as possible. If this will allow you to reduce the rate at which you render the text, you may find that performance is pretty good using this approach. The Python code can render text that changes color, font size, font, and alignment at a speed of greater than 30 fps (depends on the amount of text and size of the canvas, my code takes some time to auto-scale the font size to best fit the defined area). This appears to work well enough that I will include this along with the Pythoner example files when Isadora 4 is released.