Take it with you
If you leave, the software still belongs to you.
Custom sites and companions produced for a client are that client's property. AngelDust does not keep copyright in those files. The delivery archive includes the source and a short license that says so in plain language.
1 · During the plan
The site can run on Halo Host. Companions on your Windows or Linux machines talk to that site. You can download the source once it has been delivered.
2 · When the plan ends
Keep the archive. You do not need permission to keep using it. Hosting stops. Ownership does not.
3 · Self-hosting
Put the website folder on any web server you control. Point the Windows and Linux companions at the new address. That is a full hosting exit. You do not need AngelDust or Halo Host to keep the stack running.
What the license says
The client named on the project owns the software. The owner may copy, modify, host, and run it independently, including after a plan ends. That file ships in the same archive as the source.