Can threads use resources from other processes?
Threads are used to handle tasks simultaneously. For example, you keep your computation running in a thread, while another thread is waiting for keyboard input.

Threads inherit the privileges of the process they run in.
If the parent process is authorized to access another process's resources than the thread can do this.
The operating system assigns the process privileges when starting that process.  

Whether your threads can obtain resources or not depends on the implementation of threads in your operating systems. In Linux, with some languages such as C, your threads are able to share memory with other processes, and even threads can create other threads. Basically, threads' access to memory is the same as your process. So, threads can create a shared memory with another process and keep communicating with other processes via shared memory space.