Open Letter to Hobbyists (from Wikimedia Commons)
As you can see in the letter, it considered copying as theft, a common theme used by the copyright industries later including the word "piracy".
Now, it wasn't entirely the hobbyists' fault. MITS priced Altair BASIC so that when it was purchased with two of their 4K Dynamic RAM boards, the price was only $75, while without the hardware the price was a whopping $500. Unfortunately, dynamic RAM boards was in general problematic on the Altair (later S-100) bus for several reasons. As a result, Robert Marsh designed a 4K Static RAM board for the Altair bus and started Processor Technology to market it. Of course, those who bought that board instead of MITS's board had to pay full price. Instead, many copied the Altair BASIC from somebody else. Eventually, Ed Roberts acknowledged the problems in the October 1975 Computer Notes. The full price for Altair BASIC was reduced to $200. The price of the memory board was reduced from $264 to $195 and existing buyers got a $50 refund.