Yep. Go to Your functions, look for the function you want to share and click on Share. From then on your function is shared publicly, which means other users can search for it, find and use it. If you don't want your function to be shared anymore, you can just visit Your functions again and click on Make it private. Et voilà, privat again.
You can either browse through publicly shared functions or search for it. If you discover a function you want to use just click on Use and proceed. If you want this shared function to be one of yours, then solve and save it and Calcaas will save a copy of the function for you. Afterwards you can find it in Your functions.
What are subfunctions and how do I use them?