Python would be totally believable. Whether they were to:

• use Python just for their whiteboard pseudocode brainstorming and then later rewrite that Python in some lower-level language when actually typing the code into the computer
• use some custom middleware framework that allows them to literally code in Python, but then, like you say, automatically cross-compiles that Python into whatever embedded ancient programming language that the gate actually uses

Either of those would make more sense than using C# anywhere like they are clearly doing here.

EDIT:

import stargate  
import time  

gate = stargate.gate("username", "password")  

if gate.is_connected():  
    print("Gate connected")  
    gate.iris.open()  
    time.sleep(1)  
    if gate.iris.is_open():  
        print("Iris open")  
        gate.dial(1, 2, 3, 4, 5, 6)  
        time.sleep(1)  
        if gate.is_wormhole_established():  
            print("Wormhole established")  
            print("00:00:00.000000", end="\r")  
            time_start = time.perf_counter()  
            while gate.is_wormhole_established():  
                time.sleep(0.1)  
                time_now = time.perf_counter() -time_start  
                print(f"{time_now:%H:%M:%S.%f}", end="\r")  
            gate.iris.close()  
            time.sleep(1)  
            if not gate.iris.is_open():  
                print("Iris closed") 
                print("Program complete")  
            else:    
                print("ERROR: Could not close iris")  
        else:  
            print("ERROR: Could not establish wormhole")  
    else:  
        print("ERROR: Could not open iris")  
else:  
    print("ERROR: Could not establish connection to gate")