Audela
OS Audela is a long time running multi-OS and multilingual free software for capture and processing in astrophotography. The Sourceforge project is still active, but binary releases have become scarce.
A list of features is available here in English, but somewhat outdated compared to the French list, especially about Linux interoperability.
Audela is mainly developed in TCL, and makes great use of the scripting capability of the language to let users program their own capture sequences or processings. It also has the drawback of being a language not well known by many people, which makes it harder to understand if anything doesn't work well.
Capture
As a multi-OS capturing tool, the supported hardware differs with the OS. On Linux, there doesn't seem to be any supported telescope mount, only cameras: webcams and grabbers (probably V4L2), and QSI cameras. There may be other supported devices, but it's not explicit on the website.
On Windows, it features catalogues for many objects and is able to slew a telescope on them, guiding, image capture with settings for bias/dark/flat exposures, and so on. See the list of features.
Processing
Audela has all basic processing capabilities: working on image sequences, registration, stacking, demosaicing, wavelets and various other display or processing tools. It also has an astrometry calibration feature and some spectroscopic data reduction and analysis capabilities.