Maximum users of an application, limit license usage on Windows Terminal Server

maximum_users.ps1

# name of procsess we are tracking
$limited_process = "notepad.exe"

# limit of instances we allow
$user_limit = 3

# Limit reached message and title
$message = "Too many users! They are:"
$title = "No more notepad"

[System.Reflection.Assembly]::LoadWithPartialName("System.Windows.Forms") 
$msgbox = [System.Windows.Forms.MessageBox]
$processes = (Get-WmiObject win32_process -Filter "name='$($limited_process)'")

$users = Foreach ($proc in $processes) { $proc.getowner().User }
$names = ($users -join ', ').ToUpper()

if ($users.count -eq $user_limit) {
	$msgbox::Show("$($message) $($names)", $title)
} else {
	start $limited_process
}