I played with the Mastodon.py API and thought of an application to connect it with Bootle/Flask and then MastoShare came out. It’s a simple script, you can easily install on your webserver to add a sharing button on your website. Currently deleting authorization tokens doesn’t work, so this might be not very safe. The rest works. Note, that you have two-factor-authentication disabled while using this app (this is a bug in Mastodon.py). The source code is here.
The link to the source on GitHub ends in a 404 error.