GST on plot in joint development agreement

Yes, land developer is liable to charge/pay GST over development charges levied by him as cost of developed land/plots.

Land developer is liable to pay GST  because he has provided Works Contract Services (development services) to land owner and received developed land as consideration.

Landlord is not liable to pay GST on sale of developed plots as sale o land is neither a supply of goods nor supply of services. 

As per Sl no. (5) of Schedule III of the Central Goods and Services Tax Act, 2017, 'sale of land' is neither a supply of goods nor a supply of services, therefore, sale of land does not attract GST