How does LemmBox differ from UltraBox? LemmBox aims to expand apon UltraBox New features include:
What are some planned things I should expect to come to LemmBox soon™? Things I want to add: if you want to help, Please reach out to me on discord or on github!
How do I add custom samples? Since LemmBox doesn't have a web server of its own, you'll have to first upload your sample to a CORS (Cross-Origin Resource Sharing) -friendly website. Next, you have to copy the URL of the sound itself. The URL should end with the filetype, such as .wav or .mp3.

To import it into LemmBox, open the Edit tab, scroll to the bottom, and click on "Add Custom Samples..."

Paste your url and press "Okay." If everything goes smoothly, LemmBox will reload and your sample will be available in the preset list.
Does LemmBox have an offline version? Kind of- It does not have any executables or anything like UltraBox, but you can download everything here and it should work without an internet connection. Custom samples will not work sadly. I plan on getting this working when v1.0 comes out.
Does LemmBox claim ownership over songs created with it? LemmBox does not claim ownership over songs created with it, so original songs belong to their authors.

Neither LemmBox or its creator assume responsibility for any copyrighted material played on LemmBox. No songs are ever received, recorded, or distributed by LemmBox's servers. All song data is contained in the URL after the hash (#) mark, and LemmBox running inside your browser converts that data into sound waves.
When will x feature be added? You can track the progress of new features on the issues page.
Please be patient, I can't guarantee that anything will be out in a timely manner.
Where can I contact the developer? You can find me on many places! a few of those are, the BeepBox discord server [my username is happylemonlime] (you can join that here), the BeepBox Modding server (you can join that here), my Bluesky account (you can find that here)