Hi ErichS.
Sorry for the late reply.
1. For now, RT-Thread Studio only supports Windows, the Linux will soon come out this year.
2. FreeRTOS is supported in RT-Thread Studio, when you create a project that based on PlatformIO you'll see the FreeRTOS is there. RT-Thread Studio opens to All.
3. The sentence of Community version is free forever means RT-Thread Studio will forever free to the community. RT-Thread values its community developer very much, that's why this Studio IDE is built and it will always open to the community developer. There is no other edition.
If you have any questions while using RT-Thread Studio, you can create a post in RT-Thread Club, its community developer, and the RT-Thread technical engineers will support you.
https://club.rt-thread.io/