Due to the lack of time to continue with this project, I have decided to put it up for sale.
I don't have time enough to focus on marketing and sales or to continue extending the functions, so before letting it die, I will happily sell it to whoever wants to continue.
Income:
Since now everything is for free on the platform, I am still not having any income from this project.
Costs:
The cost of hosting the platform is also zero since everything is running on the smallest EC2 and RDS of AWS, included in the free tier. Once the first year of the free tier has passed, I estimate a monthly cost of about 35 USD if using the actual infrastructure. This can be lowered to 5 USD or 10 USD by hosting everything on an AWS Lightsails instance or Heroku.
Price:
I am open to offers.