Allen, who died in Seattle on Monday, started Microsoft with Bill Gates in 1975. He was the older of the two, and the more technically competent one.
His sister Judy said in a statement: “My brother was a remarkable individual on every level. While most knew Paul as a technologist and philanthropist, for us he was a much loved brother and uncle, and an exceptional friend.
We salute technology pioneer and Microsoft cofounder, Paul Allen, on his passing at the age of 65. Mr. Allen has been battling cancer for the past several years. Photo: Paul Allen, right, with Bill Gates in 1983. Photo credit: Doug Wilson/Corbis pic.twitter.com/GJgluMdSzm— AXICOM, Inc. (@AXICOM_Tech) October 15, 2018
"Paul’s family and friends were blessed to experience his wit, warmth, his generosity and deep concern. For all the demands on his schedule, there was always time for family and friends.
Statement from Microsoft CEO Satya Nadella on the passing of Paul Allen: pic.twitter.com/1iLDLenLKz— Microsoft (@Microsoft) October 15, 2018
Vulcan chief executive Bill Hilf said: "All of us who had the honour of working with Paul feel an inexpressible loss today. He possessed a remarkable intellect and a passion to solve some of the world’s most difficult problems, with the conviction that creative thinking and new approaches could make profound and lasting impact.
Paul Allen saved the Seahawks from relocation in 1997. He helped bring us to 3 Super Bowls, winning 1. Thank you for EVERYTHING, Paul. You are a Seattle icon forever. With tears in my eyes, Rest In Peace. pic.twitter.com/SsaFFUkA1Q— ryan leclair (@ryan_leclair) October 15, 2018
"Millions of people were touched by his generosity, his persistence in pursuit of a better world, and his drive to accomplish as much as he could with the time and resources at his disposal."
Allen owns the Seattle Seahawks and Portland Trailblazers, Stratolaunch Systems, the Allen Institute and the Allen Institute for Artificial Intelligence.
Hilf added: "Paul’s life was diverse and lived with gusto. It reflected his myriad interests in technology, music and the arts, biosciences and artificial intelligence, conservation and in the power of shared experience – in a stadium or a neighborhood – to transform individual lives and whole communities.
"Paul loved Seattle and the Pacific Northwest. The impact of Paul’s efforts can be seen here at every turn. But the true impact of his vision and generosity is evident around the globe.
He attended WSU.— 710 ESPN Seattle (@710ESPNSeattle) October 15, 2018
He helped save the Seahawks from moving to CA.
He voted to keep the Sonics in Seattle.
He helped rebuild & bring new life energy to SLU.
He helped build MoPop.
And much, much more!
He was as Seattle & PNW as they come. RIP Paul Allenhttps://t.co/mpTyyQl9Sn
"Paul thoughtfully addressed how the many institutions he founded and supported would continue after he was no longer able to lead them. This isn’t the time to deal in those specifics as we focus on Paul’s family. We will continue to work on furthering Paul’s mission and the projects he entrusted to us. There are no changes imminent for Vulcan, the teams, the research institutes or museums.
"Today we mourn our boss, mentor and friend whose 65 years were too short – and acknowledge the honour it has been to work alongside someone whose life transformed the world.”
Our industry has lost a pioneer and our world has lost a force for good. We send our deepest condolences to Paul’s friends, the Allen family and everyone at Microsoft.— Tim Cook (@tim_cook) October 15, 2018