I think I'm one of those who bought most plug out here, and have even managed objections when it comes to developers who just disappear or lay down their project!

Where did the Purusothaman Ramanujams? Has he drowned?And why not deliver Kairat Bakitow of their project over to an active developer?

"Every open source option on the web has this issue." 

A very poor excuse.

Here users worldwide maybe! paid thousands of dollars or euros, etc. for products that suddenly stops working!Is a product for free so I had not taken the time to write this article, but then it's not. 
I mean Oxwall should set the following requirements for all developers who want to post their plugin or themes for sale on Oxwall their pages:

1.Developers selling plugins or themes, and who later would be closing one project, must transfer the project free of charge to another active developer. 

2.The developer taking over the project, must also take over the customer relationship that already exists, so does the existing customer not must pay again, when a new version of the plugin or themes come out.

3.These rules should not apply plugin or themes that are free
This is the only solution to avoid that people are losing so much money! and att good project can be further developed

That such rules do not exist today, in terms of how much people have already lost money on different plugin and Themes, then such sales polisy not particularly good advertisement for all Oxwall project. 

And you have to understand that the lack of respect above their buyers wild contribute to a lackluster sales in the future. In short, this is very bad for the serious plugin and themes sellers out here.

This is bad for people who are willing to put down money on one project, they stop doing it.